Conventionally, a thermally curing adhesive, containing an epoxy resin, as a thermosetting resin, and which is cured on thermal polymerization of the epoxy resin, is used as an adhesive used for bonding objects for bonding, such as a semiconductor or a substrate, to prepare an electrical device.
For accelerating the reaction of thermal polymerization of the epoxy resin, a curing agent is routinely used in an adhesive. As this sort of the curing agent, a curing agent functioning as a polymerization catalyst for an epoxy resin, such as an imidazole compound, or a curing agent, which per se undergoes an additive reaction with an epoxy resin to form a polymer, such as a mercaptan compound or an amine compound, is widely used.
In case the imidazole compound is used as a curing agent, the adhesive may be cured in a short time. However, in this case, the adhesive needs to be heated to an elevated temperature exceeding 180° C., such that the objects for bonding may be subjected to deformation, such as elongation or bend, due to heating.
In case the amine compound or the mercaptan compound is used as a curing agent, the adhesive may be cured at a lower temperature. However, in this case, the time needed for the adhesive to be cured is longer than with the imidazole compound, thus lowering the productivity. With the adhesive cured at a lower temperature, the polymerization reaction proceeds even at an ambient temperature, and hence the adhesive is appreciably inferior in shell life. It has so far been difficult to obtain an adhesive cured at a lower temperature in a shorter time and which nevertheless has a long shell life.